The invention relates generally to a filter assembly. More particularly, the invention relates to a filter assembly including an accordion fold pack made of filter material, which is sealingly joined to a retention frame. Disposed at the end face of the retention frame, at least on one side, is a bracing whose length corresponds essentially to the length of the end-face fold. The bracing extends essentially parallel to the direction of the end-face fold edge of the accordion fold pack and is arranged in the end-face fold. European Patent 0 649 335 A1 discloses one such filter assembly. In that patent, the side walls of the accordion fold pack are in each case sealingly overlapped by a stabilizing strip. The stabilizing strip on the side facing the retention frame has a separately produced sealing strip that can be positioned against the retention frame under elastic prestressing, forming a seal. The seal between the retention frame and a filter housing surrounding the retention frame is effected by a further seal which is formed separately from the seal between the accordion fold pack and the retention frame.